Methods, systems, and apparatus for neural signal detection

ABSTRACT

Methods, systems, and apparatus for signal detection are described. In one example, a detection assembly includes a signal detector. The signal detector is configured to receive a sensor signal having a peak magnitude and a first frequency and generate an output signal having a magnitude proportional to the peak magnitude of the sensor signal and having a second frequency less than the first frequency of the sensor signal.

BACKGROUND OF THE DISCLOSURE

a. Field of the Disclosure

The present disclosure relates generally to methods, systems, andapparatus for signal detection. More particularly, the presentdisclosure relates neural signal detection methods, systems, andapparatus that utilize a circuit to measure and record the amplitude ofnerve firings along the spinal cord and peripheral nerves.

b. Background Art

Medical devices and procedures that affect or involve neural signals areknown. It is known, for example, that ablation systems are used toperform ablation procedures to treat certain conditions of a patient. Apatient experiencing arrhythmia, for example, may benefit from cardiacablation to prevent irregular heartbeats caused by arrhythmogenicelectric signals generated in cardiac tissues. By ablating or alteringcardiac tissues that generate such unintended electrical signals, theirregular heartbeats may be stopped. Ablation systems are also known foruse in treating hypertension, and in particular drug-resistanthypertension, in patients. In particular, renal ablation systems, alsoreferred to as renal denervation systems, are used to create lesionsalong the renal sympathetic nerves, which are a network of nerves in therenal arteries that help control and regulate blood pressure. Theintentional disruption of the nerve supply has been found to cause bloodpressure to decrease. Other medical devices that measure or recordneural signals include, spinal cord stimulation (SCS) systems thatprovide pulsed electrical stimulation to a patient's spinal cord tocontrol chronic pain, and cardiac rhythm management devices (CRMD) usedto regulate a patient's heart beat.

Known techniques for detecting high frequency signals in a body, andparticularly high frequency neural signals, typically require verysensitive equipment, as nerve signals differ from cardiac signals andare at a higher frequency and much narrower pulse duration. Inparticular, neural signals are typically collected through surgicallypositioned microelectrodes or micropipette electrodes. The signalsgenerated by these sensors are generally sampled by controllers at asampling rate of about four kilohertz. The sensors and controllersrequired for such techniques are not inexpensive. Moreover, some medicaldevices and procedures may benefit from limited information about neuralsignals and do not require the detailed information that is obtainedusing the known techniques.

There is a need, therefore, for neural signal detection systems that donot require expensive, surgically implanted electrodes, utilize simplerand less expensive controllers with relatively low sampling rates, andprovide useful data about detected neural signals in real time. It wouldalso be beneficial if the neural signal detection systems were compactin size so that they could be easily built into or onto an ablationcatheter, or into or onto an implantable medical device such as a spinalcord stimulator device or a cardiac rhythm management device.

BRIEF SUMMARY OF THE DISCLOSURE

In one aspect, a neural signal detector includes a rectifier circuit anda peak detector circuit operatively connected to the rectifier circuit.The rectifier circuit is configured to receive a time varying neuralsignal from a neural sensor and output a rectified signal correspondingto the received signal. The rectifier circuit is configured to receivethe rectified signal and to provide an output signal proportional to apeak magnitude of the rectified signal.

In another aspect, a detection assembly includes a signal detector. Thesignal detector is configured to receive a sensor signal having a peakmagnitude and a first frequency and generate an output signal having amagnitude proportional to the peak magnitude of the sensor signal andhaving a second frequency less than the first frequency of the sensorsignal.

Another aspect of the present disclosure is an ablation system. Theablation system includes a signal detector and a controller. The signaldetector is configured to receive, from a neural sensor, a plurality ofsignals and generate a pre-ablation output signal having a firstmagnitude proportional to a peak magnitude of at least one pre-ablationsignal of the plurality of signals and having a duration greater thansaid at least one pre-ablation signal of the plurality of signals. Thecontroller is operatively coupled to the signal detector to sample thepre-ablation output signal.

Another aspect of the present disclosure is an ablation cathetercomprising an ablation electrode, a sensing electrode, and a neuralsignal detector operatively connected to the sensing electrode. Theneural signal detector comprises a rectifier circuit configured toreceive a time varying neural signal from a neural sensor and output arectified signal corresponding to the received signal and a peakdetector circuit operatively connected to the rectifier circuit toreceive the rectified signal and configured to provide an output signalproportional to a peak magnitude of the rectified signal.

Another aspect of the present disclosure is a spinal cord stimulationdevice comprising an implantable stimulating electrode, a sensingelectrode, and a neural signal detector operatively connected to thesensing electrode. The neural signal detector comprises a rectifiercircuit configured to receive a time varying neural signal from a neuralsensor and output a rectified signal corresponding to the receivedsignal and a peak detector circuit operatively connected to therectifier circuit to receive the rectified signal and configured toprovide an output signal proportional to a peak magnitude of therectified signal.

Another aspect of the present disclosure is a cardiac rhythm managementdevice comprising a pacing lead, a sensing electrode, and a neuralsignal detector operatively connected to the sensing electrode. Theneural signal detector comprises a rectifier circuit configured toreceive a time varying neural signal from a neural sensor and output arectified signal corresponding to the received signal and a peakdetector circuit operatively connected to the rectifier circuit toreceive the rectified signal and configured to provide an output signalproportional to a peak magnitude of the rectified signal. The foregoingand other aspects, features, details, utilities and advantages of thepresent disclosure will be apparent from reading the followingdescription and claims, and from reviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of one embodiment of a signal detectionassembly.

FIG. 2 is a simplified schematic of one example signal detector for usein the detection assembly shown in FIG. 1.

FIG. 3 is a graphical representation of an example input to the signaldetector shown in FIG. 2.

FIG. 4 is a graphical representation of an example output of the signaldetector shown in FIG. 2 in response to the input shown in FIG. 3.

FIG. 5 is a simplified schematic of another example signal detector foruse in the detection assembly shown in FIG. 1.

FIG. 6 is a graphical representation of an example neural signal thatmay be detected by the detection assembly shown in FIG. 1.

FIG. 7 is an isometric view of one embodiment of an ablation systemincluding a generator, a catheter, and a return electrode.

FIG. 8 is a partial view of a distal end of the catheter shown in FIG.7.

FIG. 9 is a plan view of an example neural sensor for use in the systemshown in FIG. 7.

FIG. 10 is a schematic block diagram of a controller for use in thegenerator shown in FIG. 7.

Corresponding reference characters indicate corresponding partsthroughout the drawings.

DETAILED DESCRIPTION OF THE DISCLOSURE

The present disclosure is generally directed to methods and systems formeasuring and/or recording neural signals along the spinal cord or inperipheral nerves, including cardiac nerves and renal nerves. Themethods and systems described herein measure and/or record the amplitudeof neural signals. The systems of the present disclosure utilize asmall-sized circuit that includes generally a high frequency diode, acapacitor, and a resistor as a demodulator as described herein. In manycases, the circuitry can be sized and configured to fit inside of amedical device or on a lead or catheter. The circuitry for measuringand/or recording the activities of nerves as described herein may beparticularly useful for cardiac and renal ablation procedures, as wellas for numerous implantable medical devices as described herein.

This approach may allow an ablation catheter system to measure thesuccess of renal efferent and afferent nerve ablation during a renaldenervation procedure to provide immediate success feedback to a doctorthroughout an ablation procedure. Further, this approach may allow forspinal cord stimulator devices to provide improved sensing capabilities.Still further, this approach to measuring nerve amplitude may enableresponses from interventions between neuro and cardiac rhythm managementdevices such as the recording of nerve responses from stimulatingdifferent sites of T1-T5 and T11-L2 in the spinal cord or sites alongthe sternum and intracardiac sites. These and other benefits of thedisclosure are set forth in detail herein.

Referring now to the drawings and in particular to FIG. 1, detectionassembly 100, includes sensor 102, signal detector 104, and controller106. Sensor 102 is operable to detect a signal and generate a sensorsignal proportional to the detected signal. Sensor 102 is operativelycoupled to Signal detector 104. Signal detector 104 receives the sensorsignal from sensor 102 and generates an output signal proportional tothe sensor signal. Controller 106 is coupled to signal detector 104 toreceive the output signal from signal detector 104.

In the exemplary embodiment, signal detector 104 is configured togenerate an output signal having characteristics, such as magnitude,frequency, etc., that controller 106 is operable to sample. Inparticular, the received signal has a peak magnitude and a firstfrequency. Signal detector 104 generates an output signal with amagnitude that is proportional to the peak magnitude at a secondfrequency that is less than the first frequency. In the illustratedembodiment, signal detector 104 generates an output signal with amagnitude that is substantially equal to the peak magnitude of thesensor signal. In other suitable embodiments, signal detector 104generates an output signal with a magnitude that is greater or lesserthan, but proportional to, the peak magnitude of the sensor signal.Thus, controller 106, which may have a sampling resolution too low foraccurate sampling of the sensor signal, is provided with the outputsignal by signal detector 104, at a frequency, the second frequency,that it may accurately sample.

Referring again to FIG. 1, signal detector 104 includes rectifiercircuit 108 and peak detector circuit 110. Rectifier circuit 108receives the sensor signal, which is a time varying signal and may be analternating current (AC) signal, at input 112 from sensor 102. Rectifiercircuit 108 rectifies the received sensor signal and outputs a rectifiedsignal to peak detector circuit 110. Peak detector circuit 110 detectsthe peak magnitude of the rectified signal and generates an outputsignal with a magnitude proportional to the peak magnitude of therectified signal and the sensor signal at a frequency less than thefrequency of the sensor signal. The output signal is output from peakdetector circuit 110 and signal detector 104 via output 114. Rectifiercircuit 108 and peak detector circuit 110 may include any circuitsand/or components suitable for operation as described herein. Someexemplary rectifier circuits suitable for use as rectifier circuit 108and some exemplary peak detector circuits suitable for use as peakdetector circuit 110 are described in detail below.

The illustrated controller 106 includes processor 116 and memory device118 coupled to processor 116. Other suitable embodiments do not includeprocessor 116 and/or memory device 118. The term “processor” refersherein generally to any programmable system including systems andmicrocontrollers, reduced instruction set circuits (RISC), applicationspecific integrated circuits (ASIC), programmable logic circuits, fieldprogrammable gate array (FPGA), gate array logic (GAL), programmablearray logic (PAL), digital signal processor (DSP), and any other circuitor processor capable of executing the functions described herein. Theabove examples are exemplary only, and thus are not intended to limit inany way the definition and/or meaning of the term “processor.” Althougha single processor is illustrated in FIG. 1, processor 116 may includemore than one processor and the actions described herein may be sharedby more than one processor. Moreover, although controller 106 isillustrated in FIG. 1 as a component of detection assembly 100,controller 106 may be a part of and/or shared with another system, suchas a system with which detection assembly 100 is used.

Memory device 118 stores program code and instructions, executable byprocessor 116. When executed by processor 116, the program code andinstructions cause processor 116 to operate as described herein. Memorydevice 118 may include, but is not limited to only include, non-volatileRAM (NVRAM), magnetic RAM (MRAM), ferroelectric RAM (FeRAM), read onlymemory (ROM), flash memory and/or Electrically Erasable ProgrammableRead Only Memory (EEPROM). Any other suitable magnetic, optical and/orsemiconductor memory, by itself or in combination with other forms ofmemory, may be included in memory device 118. Memory device 118 may alsobe, or include, a detachable or removable memory, including, but notlimited to, a suitable cartridge, disk, CD ROM, DVD or USB memory.Although illustrated separately from processor 116, memory device 118may be integrated with processor 116 in other suitable embodiments.

FIG. 2 is a schematic diagram of an exemplary embodiment of signaldetector 104 with a passive rectifier circuit 108 and passive peakdetector circuit 110. In the signal detector shown in FIG. 2, input 112is configured for connection to bipolar sensor 102 (not shown). In otherembodiments, input 112 may be configured for connection to any othersuitable type of sensor 102 including, for example, a unipolar sensor102. A feed-through capacitor 200 is coupled to input 112 to pass thesensor signal to passive rectifier circuit 108. In other suitableembodiments, feed-through capacitor 200 is not included in signaldetector 104.

Passive rectifier circuit 108 in FIG. 2 is a positive half-waverectifier circuit. In other suitable embodiments, passive rectifiercircuit 108 may be any other suitable passive rectifier circuitincluding, for example, a full wave rectifier circuit, a negative halfwave rectifier circuit, etc. Passive rectifier circuit 108 includesdiode 202. Diode 202 includes anode 204 and cathode 206. Generally,diode 202 conducts current when it is forward biased, i.e., when a biasvoltage exceeding a positive threshold voltage differential is appliedacross diode 202 from anode 204 to cathode 206. Diode 202 blocks currentwhen it is reverse biased, i.e., when a bias voltage that does notexceed the positive threshold voltage differential is applied acrossdiode 202 from anode 204 to cathode 206. In FIG. 2, diode 202 may be aSchottky diode with a relatively low threshold voltage, also referred toas a diode forward voltage drop, between about 0.2 volts and 0.4 volts.In other suitable embodiments, diode 202 is any other suitable type ofdiode with a relatively low threshold voltage (e.g., less than about 0.5volts). In some embodiments, diode 202 is a germanium diode. When diode202 is forward biased, current, e.g., the sensor signal, flows throughdiode 202 to passive peak detector circuit 110. When diode 202 isreverse biased, e.g., when the voltage differential from anode 204 tocathode 206 is less than the threshold voltage, diode 202 preventscurrent from flowing between the passive rectifier circuit 108 andpassive peak detector circuit 110. Thus, only the positive portion ofthe rectified signal that exceeds the bias voltage is delivered frompassive rectifier circuit 108 to passive peak detector circuit 110.

Passive peak detector circuit 110 includes resistor 208 and capacitor210. Resistor 208 is coupled in parallel with capacitor 210. The voltageacross capacitor 210 is, via output 114, the output signal of passivepeak detector circuit 110 and signal detector 104. When current ispermitted to flow through rectifier circuit 108 to peak detector circuit110, the voltage on capacitor 210 increases as a function of the timeconstant, tau (τ), defined by the values of paralleled resistor 208 andcapacitor 210. More specifically, the time constant is equal to thecapacitance of capacitor 210 multiplied by the resistance of resistor208. Approximately when the rectified signal reaches a peak value andbegins to decrease, diode 202 becomes reversed biased, i.e., thedifference between the voltage of the sensor signal applied to anode 204of diode 202 and the voltage across capacitor 210 is less than thethreshold voltage of diode 202. Diode 202 no longer conducts current andthe voltage on capacitor 210 is discharged through resistor 208 at arate defined by the time constant. The resistance of resistor 208 andthe capacitance of capacitor 210 are selected to result in a timeconstant large enough that the voltage on the capacitor will dischargeslowly enough for controller 106 to accurately sample the peak voltageon capacitor 210. In one example implementation, controller 106 has asampling resolution of four milliseconds (ms). It is generally desirablefor peak detector circuit 110 to have a time constant greater than thesampling resolution of the controller. Accordingly, in this example,resistor 208 has a resistance of about 200 kiloohms (kΩ) and capacitor210 has a capacitance of about 33 nanofarads (nF), resulting in a timeconstant of about 6.6 ms. To change the time constant to suit adifferent sampling rate of controller 106, the resistance of resistor208 and/or the capacitance of capacitor 210 may be suitably varied.

A specific example of operation of detection assembly 100 includingsignal detector 104 as shown in FIG. 2 will be described with referenceto FIGS. 3 and 4. For this specific example, a series of pulses of 64megahertz (MHz) signals were induced on input 112 to simulate a highfrequency sensor signal. The 64 MHz signals have a period of about 15.6nanoseconds (ns). In this example, resistor 208 had a resistance of 30kΩ and capacitor 210 had a capacitance of 33 picofarads (pF), resultingin a time constant of about one microsecond (μs). FIG. 3 is a graph 300of the magnitude of induced signals 302 as a function of time. Inducedsignals 302 had a peak magnitude “P”. Rectifier circuit 108 rectifiedinduced signals 302 and provided the rectified signals (not shown) topeak detector circuit 110. FIG. 4 is a graph 400 of output signal 402 ofpeak detector circuit 110, i.e., the voltage on capacitor 210. Capacitor210 charges up to the peak voltage P of induced signals 302. When theinduced signal drops below peak magnitude 302, capacitor 210 begins todischarge through resistor 208. Because the time constant of peakdetector circuit 110 is relatively large compared to the period ofinduced signals 302, the voltage on capacitor 210 does not significantlydischarge between signals in each pulse of signals in induced signals302. Following each pulse of signals of induced signals 302, capacitor210 discharges to approximately zero volts. As a result, output signal402 is a square wave with a magnitude of approximately peak magnitude P.The period of square wave output signal 402 is significantly longer thanthe period of induced signals 302. Put another way, the frequency ofoutput signal 402 is significantly less than the frequency of inducedsignals 302. Thus, controller 106 may accurately sample output signal402 at a lower frequency and a lower sampling rate than the frequencyand sampling rate that would be required to accurately sample inducedsignals 302.

Now leaving the specific example, FIG. 5 is a schematic diagram of anexemplary embodiment of signal detector 104 with an active rectifiercircuit 108 and passive peak detector circuit 110. A sensor signal isinput to signal detector 104 through feed-through capacitor 200 at input112. Active rectifier circuit 108 receives the sensor signal and outputsa rectified signal to passive peak detector circuit 110. Passive peakdetector circuit 110 transmits an output signal through output 114.Passive peak detector circuit includes resistor 208 and capacitor 210.Active rectifier circuit 108 includes full wave rectifier 500 and buffer502. Buffer 502 is a unity gain buffer amplifier including operationalamplifier 504. Buffer 502 has a high impedance input for receiving theoutput of full wave rectifier 500 and a low impedance output to providethe output signal of full wave rectifier 500 to peak detector circuit110 with minimal losses. Full wave rectifier 500 includes operationalamplifier 506, diode 508, and resistors 510, 512, and 514. When an inputsignal, such as the sensor signal, is less than zero, full waverectifier 500 operates as an inverting amplifier with a gain of:

$\begin{matrix}{{{Inverting}\mspace{14mu}{gain}} = {- \frac{R\; 2}{R\; 1}}} & (1)\end{matrix}$where R2 is the resistance of resistor 512 and R1 is the resistance ofresistor 514. When the input signal is greater than zero, the full waverectifier has a noninverting gain of:

$\begin{matrix}{{{Noninverting}\mspace{14mu}{Gain}} = \frac{1}{1 + \left( \frac{{R\; 1} + {R\; 2}}{R\; 3} \right)}} & (2)\end{matrix}$where R3 is the resistance of resistor 510. The resistance of resistors510, 512, and 514 is selected so that the inverting gain and thenon-inverting gain are substantially equal to maintain the sameproportionality of the output signal for both positive and negativeinput signals. In one example implementation, resistor 510 has aresistance of 15 kΩ, resistor 512 has a resistance of 5 kΩ, and resistor514 has a resistance of 10 kΩ. Thus, according to equations (1) and (2),the example active rectifier circuit 108 has an inverting andnon-inverting gain of one half Other implementations may be configuredto have any other suitable gain, including a gain greater than one. Inone example implementation, operational amplifiers 504 and 506 are thetwo operational amplifiers of a LM358 dual operational amplifier anddiode 508 is a 1N4148 diode. In other implementations, any othersuitable diode and/or operational amplifiers, including two differentoperational amplifiers, may be used. It should be understood that activeversions of rectifier circuit 108 are not limited to the exemplaryrectifier circuit illustrated in FIG. 5 and rectifier circuit 108 may beany suitable active or passive rectifier circuit capable of operating asgenerally described herein. For example, active rectifier circuit 108may include a synchronous rectifier, an active half wave rectifier, adual operation amplifier rectifier, a single operation amplifier(whether full wave or half wave) with or without a buffer, etc.

The output of active rectifier circuit 108 is provided to passive peakdetector circuit 110, which operates as described above. In otherembodiments, peak detector circuit 110 is an active peak detectorcircuit 110 including one or more operation amplifiers. Active peakdetector circuits are well known to those of ordinary skill in the artand will not be further described herein.

Detection assembly 100 may be included in and/or used in conjunctionwith any system in which relatively high frequency signals are to besensed. In some exemplary systems, the detection assembly 100 is used todetect neural signals. FIG. 6 shows an example of neural signals 600. Inparticular, the neural signals 600 are muscle sympathetic nerve activityaccessed in the peroneal nerve using microneurography. Each signal has apeak magnitude and a duration. For example, signal 602 has a peakmagnitude 604, and a duration 606. The specific magnitude and durationcan vary among different nerves, different types of nerves, and amongdifferent firings of a single nerve. In general, duration 606 of a nervesignal is relatively short, e.g., one to three milliseconds. As can beseen in FIG. 6, neural signals 600 have varying magnitudes and generallyoccur stochastically and non-synchronized. Moreover, the rate of nervefirings can vary between five and five thousand firings per second.Because of the high frequency of the nerve signals, accurate detectionand reproduction of neural signals, such as neural signals 600,typically requires a relatively high sampling rate, e.g., greater thanfour kHz. For some uses as described herein, however, reproduction ofall of the details of a neural signal is not needed and/or desired. Insuch instances, detection assembly 100 may be utilized to convert thehigh frequency, time varying neural signals to lower frequency outputsignals that indicate the peak magnitude(s) of the neural signals. Thus,controller 106 may utilize a lower sampling rate to gain informationabout the neural signals than would be required to accurately sample theunmodified neural signals.

For example, in some embodiments, detection assembly 100 is included inor on, or used in conjunction with, a spinal cord stimulator (SCS). SCSpulse generators apply stimulation to the spinal cord to provide manypotential benefits. Detection assembly 100 may be used to sense neuralfiring patterns along a patient's spinal cord and peripheral nerves foruse as feedback for the SCS system, to study the efficacy of treatment,and/or for any other suitable use.

In other embodiments, the detection assembly is incorporated in or on,or used in conjunction with, a cardiac rhythm medical device (CRMD).Detection assembly 100 may be used to detect cardiac neural signals,which may be used, for example, to determine the response toneuro-stimulations. In still other embodiments, detection assembly 100may be incorporated within and/or used in conjunction with an ablationsystem, including both cardiac ablations systems and renal ablationsystems. More specifically, in some embodiments, detection system 100 isused to detect neural signals in connection with a neural ablationsystem. The detection system may be used to detect the magnitude ofneural signals before an ablation and after an ablation to facilitatedetermining the effectiveness of the ablation, and hence the overallprocedure. An exemplary ablation system incorporating detection system100 is described below. It should be understood, however, that thedetection system described above may be used with any other suitablesystem, including SCS systems, other ablation systems, CRMDs, etc. Inmany embodiments, nerve sensing electrodes including the neural signaldetectors described herein may be located close to ablation electrodesor pacing electrodes without interference.

An exemplary ablation system 700 including detection system 100 will nowbe described with reference to FIGS. 7-10. Ablation system 700 includesan generator 702, multi-electrode ablation catheter 704, and returnelectrode 706. Ablation catheter 704 is removably coupled to generator702 by cable 708. Return electrode 706 is removably coupled to generator702 by cable 710. In use, return electrode 706 is placed externallyagainst a patient's body and catheter 704 is inserted into the patient'sbody. Generally, generator 702 outputs radio frequency (RF) energy tocatheter 704 through cable 708. The RF energy leaves catheter 704through a plurality of electrodes 712 (shown in FIG. 8) located atdistal end 714 of catheter 704. The RF energy travels through thepatient's body to return electrode 706. The dissipation of the RF energyin the body increases the temperature near the electrodes, therebypermitting ablation to occur. In the exemplary embodiment set forthherein, ablation system 700 is a renal ablation system suitable for usein performing renal denervation procedures. It is understood, however,that the ablation system may be used for other treatments, includingcardiac ablation treatments, without departing from the scope of thepresent disclosure.

Generator 702 includes a user interface (UI) portion 716 for displayinginformation and notifications to an operator and receiving input fromthe user. Display devices 718 visually display information, such asmeasured temperatures, power output of the generator, temperaturethresholds, cycle time, etc., and/or notifications to the user. Displaydevices 718 may include a vacuum fluorescent display (VFD), one or morelight-emitting diodes (LEDs), liquid crystal displays (LCDs), cathoderay tubes (CRT), plasma displays, and/or any suitable visual outputdevice capable of displaying graphical data and/or text to a user.Indicators 720 provide visual notifications and alerts to the user. Inother embodiments, one or more of indicators 720 provide audiblenotifications and/or alerts to the user. In the illustrated embodiment,indicators 720 are lights, such as light emitting diodes, incandescentlamps, etc. Indicators 720 may be turned on or off, for example, toindicate whether or not generator 702 is receiving power, whether or notcatheter 704 is connected, whether or not catheter 704 (or allelectrodes 712) is functioning properly, etc. Moreover, indicators 720may indicate a quality or degree of a feature or component of ablationsystem 700, such as by changing color, changing intensity, and/orchanging the number of indicators 720 that are turned on. Thus, forexample, an indicator 720 may change color to represent a unitlessnotification of the quality of the contact between one or more ofelectrodes 712 and an artery wall, or to indicate a comparison betweenpre-ablation neural signals and post-ablation neural signals. UI portion716 includes inputs 722, e.g., buttons, keys, knobs, etc., for receivingcommands and/or requests from a user.

As shown in FIG. 8, multiple electrodes 712 may be disposed on basket724 located at distal end 714 of catheter 704. In the illustratedembodiment, basket 724 is an expandable basket that may be expanded andcollapsed by an operator of ablation system 700 to position electrodes712 against, for example, an artery wall. In the illustrated embodiment,catheter 704 includes four electrodes 712. In other embodiments,catheter 704 may include at least two, but other than four, electrodes712. A thermocouple (not shown, also referred to herein as a temperaturesensor) is attached to each electrode 712 to provide temperaturereadings of electrode 712. Catheter 704 also contains a thermistor (notshown) and a 1-Wire EEPROM. Generator 702 uses the thermistor formeasuring ambient temperature and performing cold-junction compensationon the thermocouples. The EEPROM contains a unique ID which allowsgenerator 702 to reject devices not manufactured specifically for usewith generator 702. Generator 702 also maintains usage data on theEEPROM in order to enforce maximum operation limits for catheter 704.

In the illustrated embodiment shown in FIG. 8, four sensors 102 aredisposed on basket 724 near electrodes 712. Sensors 102 may be anysensors suitable for sensing neural firings occurring near sensors 102and generating a sensor signal representative of the sensed neuralfiring. In the illustrated embodiment, sensors 102 are non-contactneural sensors; that is, neural sensors that do not require directcontact with a nerve to sense a reading or firing of the nerve. Ofcourse, other sensors that contact the nerve directly are within thescope of the present disclosure. More specifically, as shown in FIG. 9,illustrated sensors 102 are split ring neural sensors. A split ringsensor is a generally toroidal, or ring, shape split into between twoand four segments. In the illustrated embodiment shown in FIG. 9, sensor102 is a four segment split ring. Any two of the segments of the foursegment split ring may be utilized as a bipolar sensor. In the exemplaryembodiment, signal detector 104 and controller 106 are located withingenerator 702 (as shown in FIG. 10 and discussed below), and sensorsignals are transmitted, such as through a conductor within catheter704, from sensors 102 to signal detector 104 within generator 702. Inother embodiments, signal detector 104 is integrated within catheter704, and signal detector 104 output signals are transmitted, such asthrough one or more conductors within catheter 704, from signal detector104 to controller 106. In still other embodiments, signal detector 104and controller 106 are incorporated within catheter 704.

Referring now to FIG. 10, generator 702 includes a power supply 726, acontroller 728, and an RF output circuit 730. A multiplexer 740 receivesinputs from electrodes 712. Signal detector 104 receives sensor signalsfrom sensors 102 and provides its output signal(s) to controller 728.Power supply 726 receives AC power via an input 732 and converts thereceived power to a DC power output. The DC power output is provided tothe RF output circuit 730 that outputs RF power to catheter 704, andmore specifically to electrodes 712, via output 734. Controller 728 iscoupled to and controls operation of power supply 726 and RF outputcircuit 730. Controller 728 controls when and to which electrodes 712the RF output circuit 730 couples its RF power output. In otherembodiments, one or both of the RF output circuit 730 and power supply726 includes its own controller configured to control operation inresponse to commands from controller 728. In the illustrated embodiment,controller 728 also functions as controller 106. In other embodiments,controller 106 is separate from controller 728.

Controller 728 includes processor 736 and memory device 738 coupled toprocessor 736. The term “processor” refers herein generally to anyprogrammable system including systems and microcontrollers, reducedinstruction set circuits (RISC), application specific integratedcircuits (ASIC), programmable logic circuits, field programmable gatearray (FPGA), gate array logic (GAL), programmable array logic (PAL),digital signal processor (DSP), and any other circuit or processorcapable of executing the functions described herein. The above examplesare exemplary only, and thus are not intended to limit in any way thedefinition and/or meaning of the term “processor.” Moreover, although asingle processor is illustrated in FIG. 10, processor 736 may includemore than one processor and the actions described herein may be sharedby more than one processor.

Memory device 738 stores program code and instructions, executable byprocessor 736. When executed by processor 736, the program code andinstructions cause processor 736 to operate as described herein. Memorydevice 738 may include, but is not limited to only include, non-volatileRAM (NVRAM), magnetic RAM (MRAM), ferroelectric RAM (FeRAM), read onlymemory (ROM), flash memory and/or Electrically Erasable ProgrammableRead Only Memory (EEPROM). Any other suitable magnetic, optical and/orsemiconductor memory, by itself or in combination with other forms ofmemory, may be included in memory device 738. Memory device 738 may alsobe, or include, a detachable or removable memory, including, but notlimited to, a suitable cartridge, disk, CD ROM, DVD or USB memory.Although illustrated separately from processor 736, memory device 738may be integrated with processor 736.

In operation, when catheter 704 is positioned at a location for anablation, each sensor 102 detects neural signals having neural activitynear itself. These pre-ablation neural signals are transmitted to signaldetector 104, which generates pre-ablation output signals havingmagnitudes proportional to the peak magnitudes of detected neuralsignals and a frequency less than the frequency of the original neuralsignals. After an ablation has occurred at a location, post-ablationneural signals are sensed and transmitted from sensors 102 to signaldetector 104. Signal detector 104 generates post-ablation output signalshaving magnitudes proportional to the peak magnitudes of detectedpost-ablation neural signals and a frequency less than the frequency ofthe post-ablation neural signals. Controller 728 samples thepre-ablation and post-ablation output signals at a sampling frequencythat is less than the twice the frequency of the pre-ablation andpost-ablation neural signals. In other embodiments, controller 728samples the pre-ablation and post-ablation output signals at a samplingfrequency that is less than the frequency of the pre-ablation andpost-ablation neural signals. In some embodiments, the controllersamples the pre-ablation and post-ablation output signals at a samplingfrequency of about 512 Hz. In other embodiments, the controller samplesthe pre-ablation and post-ablation output signals at a samplingfrequency of about 200 Hz. In some embodiments, the controller samplesthe pre-ablation and post-ablation output signals at a samplingfrequency selected as a function of the time constant of signal detector104. After sampling the pre-ablation and/or post-ablation outputsignals, controller 728 may store the sampled signals, such as in memorydevice 738.

Controller 728 determines a difference between the magnitudes of thepre-ablation output signals and the post-ablation output signals andgenerates an indication of the determined difference. The indication maybe a visual or audible indication. For example, controller 728 maydisplay a value of the difference, e.g., an average percentagedifference, on display device 718, may display an indication of thedifference using indicators 720, may audibly announce an indication ofthe difference, etc. In some embodiments, controller 728 compares thedetermined difference to a predetermined threshold value and generatesan indication of whether or not the difference exceeds the thresholdvalue. Thus, for example, if a 75% decrease in the magnitude of theneural signals is desired for an ablation to be considered successful,controller 728 may determine whether or not the post-ablation outputsignals indicate a 75% decrease from the pre-ablation output signals. Ifcontroller 728 determines that the threshold has been exceeded,controller 728 may provide an indication, whether audible or visual,that the ablation was successful. In other embodiments, controller 728provides an indication when the ablation is unsuccessful.

Although certain embodiments of this disclosure have been describedabove with a certain degree of particularity, those skilled in the artcould make numerous alterations to the disclosed embodiments withoutdeparting from the spirit or scope of this disclosure. All directionalreferences (e.g., upper, lower, upward, downward, left, right, leftward,rightward, top, bottom, above, below, vertical, horizontal, clockwise,and counterclockwise) are only used for identification purposes to aidthe reader's understanding of the present disclosure, and do not createlimitations, particularly as to the position, orientation, or use of thedisclosure. Joinder references (e.g., attached, coupled, connected, andthe like) are to be construed broadly and may include intermediatemembers between a connection of elements and relative movement betweenelements. As such, joinder references do not necessarily infer that twoelements are directly connected and in fixed relation to each other. Itis intended that all matter contained in the above description or shownin the accompanying drawings shall be interpreted as illustrative onlyand not limiting. Changes in detail or structure may be made withoutdeparting from the spirit of the disclosure as defined in the appendedclaims.

When introducing elements of the present disclosure or the variousversions, embodiment(s) or aspects thereof, the articles “a”, “an”,“the” and “said” are intended to mean that there are one or more of theelements. The terms “comprising”, “including” and “having” are intendedto be inclusive and mean that there may be additional elements otherthan the listed elements. The use of terms indicating a particularorientation (e.g., “top”, “bottom”, “side”, etc.) is for convenience ofdescription and does not require any particular orientation of the itemdescribed.

As various changes could be made in the above without departing from thescope of the disclosure, it is intended that all matter contained in theabove description and shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

What is claimed is:
 1. A system for signal detection comprising: asignal detector configured to: receive, from a neural sensor, aplurality of signals; and generate a pre-ablation output signal having afirst magnitude proportional to a peak magnitude of at least onepre-ablation signal of the plurality of signals and having a durationgreater than said at least one pre-ablation signal of the plurality ofsignals; and a controller operatively coupled to the signal detector tosample the pre-ablation output signal.
 2. The system of claim 1 whereinthe signal detector is configured to generate a post-ablation outputsignal having a second magnitude proportional to a peak magnitude of atleast one post-ablation signal of the plurality of signals and having aduration greater than said at least one post-ablation signal, andwherein the controller is configured to sample the post-ablation outputsignal.
 3. The system of claim 2 wherein the controller is furtherconfigured to determine a difference between the pre-ablation outputsignal and the post ablation output signal.
 4. The system of claim 3wherein the controller is further configured to generate an indicationof the determined difference between the pre-ablation output signal andthe post ablation output signal.
 5. The system of claim 1 wherein thesignal detector comprises a rectifier circuit and a peak detectorcircuit.
 6. The system of claim 5 wherein the rectifier circuit isconfigured to receive the plurality of signals and output a rectifiedsignal corresponding to the peak magnitude of the at least onepre-ablation signal.
 7. The system of claim 6 wherein the peak detectorcircuit is operatively connected to the rectifier circuit to receive therectified signal and configured to provide the pre-ablation outputsignal having the first magnitude and the duration greater than said atleast one pre-ablation signal.
 8. The system of claim 5 wherein therectifier circuit comprises a passive rectifier circuit.
 9. The systemof claim 8 wherein the passive rectifier circuit includes a diode. 10.The system of claim 9 wherein the diode is a Schottky diode.
 11. Thesystem of claim 5 wherein the rectifier circuit comprises an activerectifier circuit.
 12. The system of claim 11 wherein the activerectifier circuit comprises a full wave active rectifier.
 13. The systemof claim 5 wherein the peak detector circuit comprises a passive peakdetector circuit.
 14. The system of claim 13 wherein the passive peakdetector circuit comprises a resistor coupled in parallel with acapacitor.
 15. The system of claim 5 wherein the peak detector circuitis an active peak detector circuit.
 16. The system of claim 15 whereinthe active peak detector circuit comprises at least one operationalamplifier.
 17. The system of claim 1 further comprising a neural sensoroperatively coupled to the signal detector and operable to generate theplurality of signals.
 18. The system of claim 17 wherein the neuralsensor is operable to generate the plurality of signals in response toneural signals proximate the neural sensor.
 19. The system of claim 1wherein the controller is operable to sample the pre-ablation outputsignal at a maximum sampling rate less than a frequency of the pluralityof signals.
 20. The system of claim 1 wherein the controller is operableto sample the pre-ablation output signal at a maximum sampling rate lessthan twice a frequency of the plurality of signals.